Detrital mineral geochronology and geochemistry
Wind and water are the great enemies of Earth's continents: they constantly seek to destroy and tear down topography, reducing great mountain ranges to literal piles of sand. In fact, those piles of sand (or sandstones) are sometimes the only records we have left of episodes of mountain building and other great geologic events in the deep past. Detrital mineral research seeks to interrogate individual sand grains in order to track them back to [potentially now vanished] sources and to understand the geologic history of unexplored regions.
Most detrital mineral studies involve U-Pb dating of detrital zircons. Zircon ages provide a good baseline on the igneous history of the source region but they tend to miss the metamorphic history of the source region. We also cannot tell based on age alone what kind of rock the zircon originally came out of. However, we can date other U-bearing minerals and we can also look at the trace element compositions of both zircons and these other minerals in order to better understand what kind of lithologies they were originally derived from. To this end, I have set up methods in the laser lab here to simultaneously measure both U-Pb age and key trace element ratios in zircon, monazite, rutile, and titanite by LA-ICP-MS. A pilot study has recently been published in G-Cubed and involves sand from the Merrimack River in New England. The figure below summaries the findings and the individual layers of information that are provided by the different minerals.